The present invention relates to a sandwich composite having a high insulation capacity and the ability to withstand high impact loads. More particularly, the present invention relates to a sandwich composite material composition that can be used to insulate shipping containers used for transporting temperature sensitive products.
Insulated shipping containers are used to ship temperature sensitive products such as pharmaceuticals, food and chemicals. The shipped product or payload must be maintained within a predetermined temperature range during transport. The insulation material used for the container dictates the duration of time in which the payload can remain within a predetermined temperature range. The structural component (usually an outer shell) of the container protects the payload from damage and maintains integrity of the insulation material from any physical impact.
The industry standard package design includes sheets of insulation material that are placed inside a corrugated cardboard container. The most commonly used insulation materials are expanded polystyrene (EPS) and polyurethane (PUR). The insulation materials are typically two to three inches thick and, because of this, limit the amount of volume available for payload, thereby increasing the number of containers needed and overall packaging cost. If the insulation material can be made thinner without compromising the insulation capacity, the usable volume of the container increases and the overall efficiency of the packaging solution improves. Further, insulation materials that have improved load bearing capacity can negate the need for additional structural support and can provide flexibility in container design.
The insulation material, by virtue of its low heat transfer capacity, reduces the rate at which the payload gains heat from the surrounding environment. The lower the thermal conductivity of the insulation material, the longer the container can hold the payload in the predetermined temperature range. The thermal conductivity of EPS and PUR is in the range of 30-40 mW/mK. To increase temperature hold time, temperature sensitive payloads are typically packed with other cooling materials like wet ice, dry ice or phase change materials. The cooling materials work in tandem with the insulation, absorbing the excess heat which enters the container and helping maintain the payload temperature within the predetermined temperature range.
The major drawback with the use of cooling materials is that the materials increase the dead weight of the package. Therefore, a low thermal conductivity insulation material can significantly lower the amount of cooling materials needed to protect the payload. With their limited insulation capacity, both EPS- and PUR-insulated containers have a payload temperature hold time of about forty-eight hours. A container with a better insulation rating will prolong the temperature hold time for the payload, reduce the amount of cooling material required, and improve the overall efficiency of the packaging solution.
Further, because EPS and PUR have a porous microstructure, each material has very low compressive strength and bending stiffness. And due to their fragile nature, the insulation materials are easily prone to physical damage which further reduces insulation capacity. Low compressive strength and bending stiffness, and overall fragility, limits the formability and application of these materials. Additionally, the existing design of EPS- and PUR-insulated containers is not durable and limits the reusability of the container solution for a new payload.
Therefore, a need exists for a thin, lightweight, high impact resistant insulation material that can be formed into a highly durable multi-use shipping container for efficient and safe transportation of temperature sensitive payloads.